The present invention relates to magnetic random access memory devices, and more specifically, to magnetic random access memory with a synthetic antiferromagnetic (SAF) freelayer with a non-exchange-coupled spacer layer.
SAF storage layers are implemented in magnetic random access memory devices (MRAM) with certain advantages. For example, it appears that higher activation energy can be obtained for equivalent switching currents when using a SAF structure versus a simple single free layer. Currently, the results in the literature that demonstrate such advantage are obtained with low-temperature annealing and processing. However, for many semiconductor applications (particularly for embedded memory application) it is important that the process be compatible with existing CMOS fabrication requirements. In practice, this means that the MRAM device must be able to withstand high temperature annealing and processing, with temperatures in the range of 400° C. for 1 hour total exposure time. Currently, it is also possible to fabricate SAF structures, which survive 400° C. anneals, demonstrating strong coupling in the SAF. Spin torque switching has been observed for anneal temperatures of up to 350° C. However, the current density can be too large to be practically employed, and even for these demonstrations the activation energy reported was only 62 kT. For applications in MRAM, an activation energy of at least 80 kT is typically required in order to retain information for sufficiently long times.